<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    li{
      height: 50px;
      background-color: #fc8;
      margin-top:5px;
    }
  </style>
</head>
<body>
  <div id="app">
    <button @click="addLi">增加li</button>
    <ul class="oul">
      <li v-for="item in arr" :key="item">
        {{ item }}
      </li>
    </ul>
  </div>
  <script src="./vue.js"></script>
  <script>
    const vm = new Vue({
      el: '#app',
      data: {
        arr: [1,2,3,4]
      },
      methods: {
        addLi(){
          this.arr.push(this.arr.length+1);
          this.$nextTick(()=>{
            // 在每一次 真实dom 更新完毕后触发
            
            const oul = document.querySelector('.oul');
          console.log(oul.children);
          })
          // const oul = document.querySelector('.oul');
          // console.log(oul.children);
         
        }
      }
    })

  
  </script>
</body>
</html>